Determination of the chemical diffusion coefficient of Li + in intercalation-type Li 3V 2(PO 4) 3 anode material

Abstract

The chemical diffusion coefficients of lithium ion ( D Li + ) in intercalation-type Li 3V 2(PO 4) 3 (LVP) anode material as a function of cell voltage between 3.0 and 0.0 V are systematically determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The true chemical diffusion coefficients ( D Li + true) obtained from EIS and GITT for the single-phase region (1.6–0.0 V vs. Li +/Li) are in the range of 10 −10 to 10 −9 cm 2 s −1 and 10 −11 to 10 −10 cm 2 s −1, respectively, and exhibit a decreasing trend of the change of D Li + true vs. voltage as the discharge and charge proceeded. The apparent chemical diffusion coefficients ( D Li + app) measured from CV and GITT for the two-phase regions (around 2.5–1.6 V) are in the range of 10 −10 cm 2 s −1 and 10 −12 to 10 −10 cm 2 s −1, respectively. For GITT, D Li + app vs. voltage plots display a characteristic of “W” shape due to the strong interactions of Li + with surrounding ions. Finally, the D Li + values of LVP anode are compared with other anode materials, illustrating that LVP can also be used as a potential anode material to achieve high rate capability.